They recently stated that the ending isn't gonna be what we'll expect it to be and that Azshara has actually imprisoned N'Zoth and they're not working together anymore.
So what I think is gonna happen is this.
We'll find out that the one, that whispered to Vol'jin and made him pick Sylvanas as the next warchief, is N'Zoth and he did it because he thought Sylvanas was easily corruptable and could be used to fight Azshara and therefore free himself from her.
As we march into Nazjatar our heroes will realize this, tensions between the Alliance and the Horde will ease up in the face of a new, stronger villain, and the Alliance and the Horde, instead of killing Azshara, will ally with her (at least temporarily) and together they will defeat N'Zoth.
The expansion will end with all three empowered, female warbringers - Jaina, Sylvanas and Azshara - defeating N'zoth. Feminism will destroy toxic masculinity. Baine, Anduin and Nathanos will be male allies.